This application claims the priority of German Patent Application No. 198 15 311.2, filed Apr. 6, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a securing arrangement for a steering wheel lock which is fastened to a steering column tube of a steering system of a motor vehicle and has a steering-column-tube-side receiving device on which a lock housing is fastened, the receiving device and the lock housing having aligned bores which are penetrated by a securing bolt, the securing bolt being at least almost completely surrounded by the receiving device, the lock housing, or both.
A securing arrangement of this type is disclosed by German Patent Document DE 23 66 072 B2. The steering wheel lock has a lock housing which is fastened by means of a securing bolt on a receiving device of the steering column tube. The securing bolt has a slidable design and is loaded by a coil spring in its release direction and by an elastic disk in its locking direction, which elastic disk can be operated from the outside by means of a tool. The elastic disk can exercise higher forces on the securing bolt than the coil spring in order to be able to hold the securing bolt in its locking position.
European Patent Document EP 0 094 568 A2 discloses another securing device for a steering wheel lock in which lock housing can be fastened by a locking pin in a steering-column-tube-fixed receiving device.
German Patent Document DE 36 26 014 C2, corresponding to U.S. Pat. No. 4,854, 142, discloses a securing arrangement which has a first housing part fixedly connected with the steering column tube of a motor vehicle steering shaft, and onto which a second housing part is fitted. A control rod for a lock bolt is guided in the two housing parts, which lock bolt engages in a locking position in a steering shaft detent ring fixed to the steering shaft and blocks a rotation of the steering shaft in this manner. The housing parts have mutually overlapping sections through which aligned bores extend in which a securing bolt is guided. In a center area, the securing bolt has a recess in which the lock bolt engages particularly when it is in its locking position blocking the steering shaft. In this position of the above-mentioned securing arrangement, the securing bolt is form-lockingly secured with respect to an axial displacement so that it cannot be removed. On one side, the securing bolt has a screw thread which protrudes out of the housing parts and onto which a nut is screwed for securing purposes.
It is an object of the invention to provide a securing arrangement of the initially mentioned type which ensures a reliable authorized removal possibility, on the one hand, and a secure disassembly protection against a violent intervention, on the other hand.
This object is achieved in that the securing bolt has a first non-circular section to which a lock bolt, which can be moved between a locking position and a release position, is applied in a form-locking manner outside its release position and blocks the securing bolt, the securing bolt being arranged to be rotatable between a displacement position, in which it can be removed from the lock housing, and a detent position, in which it is blocked on a housing-fixed stop. In this case, the application surfaces, which the securing bolt exhibits to the outside, are reduced to a minimum, the faces being lowered into the housing so that, in particular, a violent driving-through of the securing bolt in its axial direction is largely prevented by the housing. In addition, a reaching around the securing bolt is excluded. An unauthorized removal of the steering wheel lock is therefore prevented. The securing bolt has a basic shape that is essentially cylindrical. The non-circular section deviates from this shape and preferably has one or several plane application surfaces. The lock bolt can form-lockingly be applied to such a section and can prevent a rotation and/or an axial displacement of the securing bolt. As result, a double fixing for the securing bolt in the detent position of the securing bolt can be achieved on the one hand because the lock bolt as well as the housing-fixed stop can prevent an axial displacement of the securing bolt. On the other hand, the securing bolt can be removed from the locking housing only in its displacement position which it reaches by a rotation starting from the detent position which cannot be managed by violent means or is very difficult to manage because of the form-locking application of the lock bolt on the non-circular section of the securing bolt.
As a further development of the invention, the securing bolt has as a first non-circular section a recess into which the lock bolt engages outside its release position, the lock bolt also having a recess into which the securing bolt engages outside its detent position, whereby the lock bolt is blocked in the release position. As a result, no engagement occurs between the lock bolt and the securing bolt precisely when the lock bolt is in its release position and the securing bolt is in its detent position. Optionally one of the two blocking elements can be moved out of this so-called "neutral position", whereby the other element is blocked.
In a further development of the invention, the securing bolt has a second non-circular section with a projection which projects eccentrically to an axis of rotation and to which a housing-fixed stop is assigned. The projection protrudes over the cylindrical surface of the securing bolt so that the projection of the securing bolt can strike against the stop in the circumferential direction and/or in the axial direction of the securing bolt. As the result of a slide-in opening in the housing, the stop may be constructed with a cross-section corresponding to the second non-circular section of the securing bolt, so that an axial stop is obtained which acts outside the displacement position of the securing bolt.
In a further development of the invention, the radially projecting protrusion is constructed as a bolt head on a face of the securing bolt which is arranged in a receiving pocket. The receiving pocket has two mutually opposite walls between which the bolt head can be inserted in a precisely fitting manner. As a result, an axial stop can be obtained which acts on two sides for the complete fastening of the securing bolt.
In a further development of the invention, tool application surfaces are provided on a face of the securing bolt which are dimensioned such that forces which can be generated by an applied tool are lower than the counterforces defined by the form closure of the securing bolt and/or of the lock bolt. The tool application surfaces preferably represent the only possibility for operating the securing bolt and simultaneously form a desired breaking point or a force limiting arrangement. In the event of a violent intervention, the tool application surfaces are destroyed but not the important parts of the securing arrangement arranged in the housing. Furthermore, the tool application surfaces in conjunction with the enclosed accommodation of the securing bolt in the lock housing, by limiting the size of the applied tool, can also be used for limiting the forces which can be maximally introduced.
In a further development of the invention, the tool application surfaces are arranged within a recess in the face of the securing bolt. As a result, the securing bolt can be rotated only by means of those tools which can be fitted into the recess. The torque which can be maximally introduced can therefore be estimated by means of the provided tool cross-section and the securing bolt can be dimensioned correspondingly.